A proton nuclear magnetic resonance investigation of biologically relevant electronic structural and dynamic properties of paramagnetic model compounds for the active sites of hemo-proteins is in progress. The use of synthetic porphyrins will permit a characterization of the metal-porphyrin and metal-axial-ligand bond as a function of metal ion. The nature of the iron-porphyrin and iron-imidazole bonding as a function of iron oxidation state, spin state and stereochemistry will be elucidated as an aid towards understanding the changes in bonding upon oxygenation of hemo-proteins. The influence of systematic, controlled perturbations on the paramagnetic shifts of the model compounds will be analyzed to form a basis for interpreting the observed shift variations in hemo-proteins. The utility of diastereotopic methylene proton splitting as a probe for the extent of metal ion displacement from the heme plane will be assessed. A series of NMR kinetic studies will be initiated to aid in assessing the importance of rate-controlling bond-rupture mechanisms in hemo-proteins, estimates of the mobility of out-of-plane metal ions relative to the porphyrin plane by monitoring porphyrin "inversion", and yield kinetic and mechanistic data on porphyrin electron transfer reactions. BIBLIOGRAPHIC REFERENCES: "C-13 NMR Spectra of Aflatoxin B1 Derived from Acetate", D. P. H. Hsieh, J. N. Seiber, C. A. Reece, D. L. Fitzell, S. L. Yang, D. I. Dalezios, G. N. La Mar, D. L. Budd and E. Motell, Tetrahedron 31, 661 (1975). "Biosynthesis of Averufin from Acetate by Aspergillus Parasiticus, D. L. Fitzell, D. P. H. Hsieh, R. C. Yao and G. N. La Mar, J. Agric. Food Chem. 23, 442 (1975).